This invention relates to a hand-held saw for cutting the shielding or armor of a shielded conduit such as BX cable and the like and, in particular, to a saw which permits clamping and cutting of conduit of various diameters.
A manual tool for cutting shielding of conduit is disclosed in U.S. Pat. No. 3,851,387 and has successfully replaced the use of hacksaws and other unguided cutting tools for this task. This hand tool permits shielded conduit to be securely held while a radial cutting blade cuts through and severs one or more convolutions of the shielding in a direction generally parallel to the longitudinal axis of the conduit. Once a single convolution of the shielding is completely severed, the shielding at the end of the conduit can be easily removed to expose the insulation and the wires below to make the electrical connections desired. The hand tool holds the cutter head in a rigid and fixed relationship to the shielding while at the same time guarding against injury to the operator and damage to the wires inside the conduit. Improvements to this hand tool have been disclosed in U.S. Pat. Nos. 4,142,290 and 4,359,819, and 4,769,909.
Although the conduit cutting hand tools disclosed in the aforementioned patents work efficiently, they are generally designed to secure only limited range of diameters of shielded conduit. Accommodating both large and small conduit becomes difficult because, for conduit up to about 2 inches in diameter, the larger the diameter of such conduit, the larger is the width of the individual convolutions in the direction of the longitudinal axis of the cable. In order to sever a very wide convolution on a large diameter cable, it is necessary to either utilize a large diameter radial cutting blade or, when utilizing a smaller cutting blade, to move the cutting blade relative to the cable to effect a longer cut in the direction of the conduit axis. The former suggestion is generally impractical since the larger diameter blade will make a deeper cut into the cable with more chance of cutting into the electrical wires therein. The latter method of moving the cutter head relative to the cable has been disclosed in U.S. Pat. No. 4,142,290. However, the mechanism disclosed therein moves the cable relative to the entire hand tool and has not proved practical to accommodate both large and small diameter cables.
Bearing in mind the unsolved problems of the prior art, it is therefore an object of the present invention to provide a saw for cutting shielded conduit which may accommodate both large and smaller diameter conduit.
It is another object of the present invention to provide a hand held saw for cutting conduit which is relatively simple in design and easy to operate.
It is a further object of the present invention to provide a saw for cutting large diameter shielded conduit which permits a single convolution in the armor of shielded conduit to be cut in a single step.
It is yet another object of the present invention to secure the cable in a fixed position relative to the tool during the entire cutting process.